Kinase Family PLK

PLK has three subfamilies, based on evolutionary conservation. PLK1 and PLK2 are similar both in their kinase domains and in having two polo boxes, domains which are unique to polo kinases. PLK1 is found in metazoans, while PLK2 is restricted to deuterostomes. The SAK gene has just one divergent polo box (not usually recognized by Pfam profiles), and is also more divergent in its kinase domain. A number of so-far-unclassified polo kinases are found in unicellular eukaryotes, but none is found in plants.